In video and image compression systems, the processing of pictures may be performed in blocks of pixels, where the blocks of pixels to be processed may be of different sizes. These block-based image and video compression systems may exhibit “blocking” artifacts at the boundaries between picture blocks or macroblocks. The blocking artifacts may occur from the independent transformation and quantization of adjacent macroblocks that may result in the better reproduction of low frequency coefficients in some macroblocks than what is achieved in other macroblocks. When the macroblocks are reconstructed to reproduce the original picture, there may be a slight low frequency offset between adjacent macroblocks that may result in visible artificial edges. The intensity of the visible artificial edges may depend on the content and/or the bit rate associated with the reconstructed pictures. In order to reduce the effects of visible artificial edges in a reconstructed picture, video and image compression systems may utilize deblocking filters.
Some compression standards, for example, JPEG, MPEG-1, MPEG-2, MPEG-4 simple profile (SP), MPEG-4 advanced simple profile (ASP), and H.261, do not specify how to reduce the effects of blocking artifacts in a reconstructed macroblock or picture. In this regard, a specification is not provided either for macroblocks reconstructed in a decoder or in a decoding portion of an encoder. Systems that utilize standards that do not specify deblocking filters may be referred to as Type A compression systems. In Type A compression systems, a deblocking filter may be utilized to reduce visible artificial edges only as a non-normative post-processing step. For example, in video decoders, a deblocking filter may be utilized as a non-normative post-processing step before transferring the reconstructed pictures to be displayed by a display engine.
Other compression standards, for example, H.263 and H.264/MPEG Advanced Video Coding (AVC), may specify the utilization of a normative in-loop deblocking filter that may operate on reconstructed macroblocks that make up a reconstructed picture to remove or reduce visible artificial edges. In-loop may refer to filtering that is part of the coding or decoding operations. In this regard, the deblocking filter may be utilized in a decoder or in the decoding portion of an encoder before transferring the reconstructed picture to another component or device for further processing. Systems that utilize standards that specify in-loop and/or out-of-loop deblocking filters may be referred to as Type B compression systems.
In another example, the VC-1 advanced video codec standard may specify a normative in-loop deblocking filter. Moreover, the VC-1 advanced video codec standard may also recommend the use of an out-of-loop deblocking filtering in a decoder. In this regard, out-of-loop may refer to filtering that is not part of the coding or decoding operations. A compression system that supports the VC-1 advanced video codec standard may operate as a Type A compression system, for example, when utilizing the out-of-loop deblocking filter or as a Type B compression system, for example, when utilizing a normative in-loop deblocking filter.
The architectural and operational differences between Type A and/or Type B compressions systems, whether they are encoders, decoders, and/or encoder/decoder (CODEC) pairs, may be of significance because new integrated circuit (IC) video compression systems may be required to provide support to multiple compression standards in a single system-on-chip (SOC) solution. The cost associated with multi-standard IC video compression systems in a single SOC solution may be high because of the large chip area that may be required to provide the necessary encoders, decoders, and/or CODECs to support multiple standards in a single integrated circuit.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.